The invention is directed to a method for automatic character recognition.
In contrast to character recognition by man, who normally does not view the characters of a character string in isolation but places them into contextual relationship with the neighboring characters, for a long time automatic character recognition was exclusively limited to the recognition of discrete characters. Despite what has become a high recognition reliability in discrete character classification, it has quickly become evident that a further performance enhancement is only possible when the context is involved in the recognition process. With the assistance of the context, substitutions and rejections (i.e. characters that were incorrectly recognized or not recognized at all) can be recognized as errors and may also be subsequently corrected in a fashion coming extremely close to human perception.
A known context method (see VDE-Fachberichte, 30/1978, pages 195 through 206, incorporated herein by reference), for example, provides that the character classifier respectively offers a plurality of alternatives for characters of a character string that were not clearly recognizable, a series of alternative character strings being then formed therefrom. Finally, these alternative character strings are compared to permissible words that were previously deposited in a lexicon memory, whereby the alternative character string coinciding with a permissible lexicon word is ultimately selected. Although the recognition reliability can be fundamentally enhanced in this way, such a method has the disadvantage that only character strings whose legitimate comparison words were stored in the lexicon can be corrected in this way.